Allow homoicon's local copy of sobek in the canonical .golangci.yml (closes #134)

The comment above the gomoddirectives exclusion now names sobek and
homoicon in plain sentences, links sneak's decision and says why this is
an exclusion. TODO.md gains the dated Completed Steps entry. The rule
itself is unchanged: a local replace of github.com/grafana/sobek in a
repository's root go.mod passes, and every other local replace is still
refused.

Model: opus-5-5

.golangci.yml

@@ -97,9 +97,11 @@ linters:
           reason: "Unmaintained fork; use go-udiff."
   exclusions:
     rules:
-      # homoicon keeps a local copy of the JavaScript engine (sneak's decision,
-      # https://git.eeqj.de/sneak/homoicon/issues/1759#issuecomment-153261).
-      # Excluded, as gomoddirectives' replace-allow-list skips local paths.
+      # homoicon keeps a local copy of sobek, its JavaScript engine, as sneak
+      # decided in
+      # https://git.eeqj.de/sneak/homoicon/issues/1759#issuecomment-153261.
+      # This is an exclusion because gomoddirectives does not check its
+      # replace-allow-list for a replace that points at a local path.
       - path: ^go\.mod$
         linters:
           - gomoddirectives